The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
(1) Field of the Invention
This invention generally relates to an underwater high speed projectile speed sensing device for the adaptable high speed underwater munition (AHSUM) project. More particularly, the invention relates to a sensing circuit for providing a state output of wire coils used in the testing of an underwater projectile.
(2) Description of the Prior Art
The known Adaptable High Speed Underwater Munition (AHSUM) project needed a method to sense the speed of underwater projectiles during the course of their test series, and particularly a calculation of the velocity of a projectile traveling at high rates of speed in an underwater firing range.
Some of the unique aspects of testing an underwater projectile include the presence of a conducting medium and highly variable projectile paths caused by the liquid medium.
It is also desirable to measure the projectile""s deceleration toward the end of the range.
The following patents, for example, disclose various types of voltage coils and velocity measuring systems, but do not disclose a device for sensing projectile velocity using a voltage coil and sensing circuit according to the aspects of the present invention.
U.S. Pat. No. 2,206,927 to Turnbull et al.;
U.S. Pat. No. 3,127,768 to Mason;
U.S. Pat. No. 3,659,201 to Vogelsang;
U.S. Pat. No. 3,824,463 to Oehler;
U.S. Pat. No. 4,845,690 to Oehler;
U.S. Pat. No. 4,483,190 to Cornett;
U.S. Pat. No. 4,649,796 to Schmidt; and
U.S. Pat. No. 5,233,901 to Nilsson et al.
Specifically, the patent to Turnbull et al discloses a device for detecting the emergence of a projectile from the muzzle of a gun barrel. More specifically, the device uses the electric charge found in the powder gasses and on the metallic parts of guns for changing the electrical potential of devices therein or connected thereto, and securing desired indicia therefrom.
The patent to Mason discloses an electronic method for obtaining velocity and pressure characteristics of firearms and of bullets or shells fired therefrom. The bullet fired from a gun is directed through the coils of at least two sensing members which have been connected to a high frequency oscillating circuit. A signal from the oscillating circuit is transmitted to gate means and from the gate means to a computer. A separate high frequency oscillating current is applied to the computer while simultaneously obtaining an amplified signal from a pressure transducer mounted on the rifle to a second computer, whereby signals obtained from the same rifle and the same explosion therefrom indicate velocity and pressure factors of the rifle bullet as fired from the rifle.
Vogelsang discloses an apparatus for measuring the muzzle velocity of a projectile which has a measuring system at the muzzle of the gun barrel. The measuring system has two relatively spaced coils though which the projectile passes for inducing two signal pulses. Means are provided for compensating for changes in the distance between the two coils due to variations of temperature including a temperature-dependent resistor and wherein the thermoelectric voltage measured across the resistor is used as a compensating voltage in an electronic compensating circuit. The electronic compensating circuit has a phase-inverting stage to which the signal pulses are to be applied wherein the output of the phase-inverting stage is connected to the input of a modified mono-stable multi-vibrator.
Oehler discloses a shot cluster velocity measuring apparatus in which the coils through which the shot is to sequentially pass are mounted in axially spaced relation and are electrically connected as frequency determining elements in a high frequency oscillator, the output of which is frequency modulated as the shot cluster passes the coils. An FM discriminator generates an amplitude varying signal representative of the frequency modulation. A differentiating and filtering circuit shapes the discriminator output which is then amplified. The gain of a variable gain amplifier is automatically adjusted to equalize signal amplitude, and a Schmitt trigger produces rectangular pulses. If the pulses out of the trigger are of sufficient duration they are used to produce xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d signals, indicating the passage of the center of mass of the projectile or projectile cluster through the first and second coils, respectively. These signals are then used to control an interval timer which displays the count as a measure of velocity.
The patent to Cornett discloses a muzzle velocimeter having a pair of sensors positioned adjacent to the path of a projectile containing magnetic material wherein each of the sensors includes a permanent magnet having a wire coil wound thereon. The magnets provide magnetic fields which are disturbed by magnetic materials in a passing projectile causing each of the sensor coils to develop signal pulses. The distance between the sensor coils and the amount of time between the sensor coil pulses are used to calculate the velocity of the passing projectile. In an alternate embodiment a single sensor coil is used to sense the leading and tailing edges of a passing projectile and the projectile velocity calculated by using projectile length and passing time of the projectile.
The patent to Schmidt discloses a method and apparatus for setting a projectile fuse during muzzle exit. A transmitted coil concentrically mounted to the gun muzzle is utilized both to sense the presence of the projectile at the gun muzzle and to inductively transmit a radio frequency signal having a duration proportional to the fuse time delay value to a receiver coil disposed on the projectile. The transmitter coil is energized from a radio frequency oscillator before the projectile is fired. As the font end of the projectile begins to emerge from the gun muzzle, its presence is detected by a change in the transmitter coil impedance, and the transmitter coil is automatically de-energized. The receiver coil is spaced from the front end of the projectile so that it is not inductively coupled to the transmitter coil, the transmitter coil is re-energized from the oscillator for a time period proportional to the fuse time delay value to be set, then again de-energized until the projectile has completely emerged from the gun muzzle. The signal received by the receiver coil is processed by circuitry within the projectile to set the fuse time delay value.
The patent to Nilsson et al. discloses an apparatus for determining the roll angle of a rotating projectile shell, missile or the like as it leaves the barrel or launch tube which includes a magnetized part with a known polarization direction provided in the projectile, and two pairs of windings mounted at the very front of the muzzle bell of the barrel in such a way that a voltage is induced in the windings when the projectile passes the mouth, and an evaluation unit is designed to calculate, based on the voltage signals, the roll angle position of the projectile upon firing.
However, the prior art does not teach a velocity measurement system specifically adapted to measure the velocity of a high speed underwater projectile.
Therefore it is an object of this invention to provide a device for sensing projectile velocity.
Another object of this invention is to provide a device for sensing projectile velocity in an underwater environment.
Still another object of this invention is to provide a device for sensing projectile velocity in an underwater environment which allows a wide range of movement by the projectile.
A still further object of the invention is to provide circuitry which is an accurate and inexpensive method to measure the velocity of a projectile under the water.
Yet another object of this invention is to provide a device for sensing projectile velocity in an underwater environment which is simple to manufacture and easy to use.
In accordance with one aspect of this invention, there is provided a device for sensing projectile velocity in an underwater environment. The device includes a plurality of evenly spaced voltage coil members positioned in a path of the projectile. Each voltage coil member includes a support member having an opening therein, a voltage coil surrounding the opening of the support member, and a sensing member correspondingly connected to each voltage coil. The sensing member includes means for outputting a signal responsive to the passage of the projectile through the voltage coil member, and a logic arrangement for determining a difference between passage of the projectile between adjacent ones of the plurality of voltage coil members, thereby determining a velocity of the projectile.